This invention relates to sample cells designed to receive for optical analysis a flowing sample of liquid suspended particles. When it is desired to measure the total volume of the particles in the sample or their volume distribution, it is necessary to use two analytical systems when the particle sizes range widely as from 0.1 microns to a size beyond 10 microns. It is known, for example, that the use of an analytical system such as that disclosed in U.S. Pat. No. 3,873,206 issued to William Leslie Wilcock on Mar. 25, 1975 can be utilized to measure the volume of particles in the range of 2.0 to 100 microns by measuring the forward scattered light produced by a light beam incident to the sample when an appropriate spatial filter is used. It is also known that the analytical system of U.S. Pat. No. 4,134,679 issued to the present inventor on Jan. 16, 1979 can be utilized to measure the volume of particles in the range of 0.1 to 10 microns in diameter by measuring the light scattered by the particles at 90.degree. from the axis of an incident beam whose wavelength is twice the diameter of the particles being measured when the measurement uses two orthogonal polarizations. U.S. Pat. Nos. 3,873,206 and 4,134,679 are hereby incorporated by reference as a part of this specification.
In order to efficiently use the two above mentioned analytical systems to measure particle volume in the range of 0.1 to 100 microns without the necessity of using two separate instruments with the inevitable difficulties involved in coordinating the results and avoiding expensive duplication, it is necessary to make the two measurements, that is the forward scattering and the 90.degree. scattering measurements at the same time, or in a short time span making any necessary computations later.
It is therefore an object of this invention to provide a sample cell whose structure will make possible the measurement of the forward scattered light and the 90.degree. scatter in two orthogonal directions without the introduction of wells, insertions, or bends in the sample stream which can create turbulence.